Apparatus and method for mixing fluids

ABSTRACT

Apparatuses and methods for mixing a first fluid with a second fluid are described herein. One such apparatus includes a chamber that contains the first fluid and the second fluid. The apparatus also includes a piston that is positioned within the chamber and that is movable within the chamber. The piston can move back and forth to mix the first fluid and the second fluid together. The apparatus further includes a restrictor that provides for controlled movement of the piston and thus protects the piston and other components of the apparatus during operation.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit of U.S. Provisional Application Ser. No. 61/868419 filed August 21, 2013, which application is incorporated herein, in its entirety, by reference.

TECHNICAL FIELD

This disclosure relates to mixing fluids and, more particularly, to an apparatus for mixing fluids.

BACKGROUND

Mixing devices can be used to mix two different types of fluids together downhole within a wellbore tool. More specifically, a mixing device can be used to create a mixture between a reactant and a formation fluid. The reactant can be used to detect a particular chemical within the formation fluid. In one example, the reactant is a fluid that is selected to detect hydrogen sulfide (H₂S) within the formation fluid by reacting with the hydrogen sulfide and producing a detectable optical characteristic. Accordingly, the mixing device can be used to generate a mixture by thoroughly mixing the reactant with the formation fluid. This mixture can then be analyzed optically to determine the presence of a particular chemical within the formation fluid. To facilitate this optical analysis, often the mixing device generates a homogenous mixture between the reactant and the formation fluid.

SUMMARY

Illustrative embodiments of the present disclosure are directed to a wellbore tool for mixing a first fluid with a second fluid. The wellbore tool includes a chamber with a first end, a second end, a first opening at the first end, and a second opening at the second end. The tool also includes a piston positioned within the chamber. The piston generates a seal between the first end and the second end of the chamber and is movable along the chamber towards the first end and towards the second end of the chamber. The tool further includes a restrictor positioned at the first end of the chamber. The restrictor allows the flow of fluid through the first opening and into the chamber and partially restricts flow of fluid through the first opening and out the chamber. Furthermore, the tool also includes a perforated piston positioned within the chamber between the piston and the second end of the chamber. The perforated piston includes a bottom surface, a top surface, and one or more channels that allow fluid to flow between the top surface and the bottom surface of the perforated piston.

Various embodiments of the present disclosure are also directed to a downhole method for mixing a first fluid with a second fluid within a chamber. The chamber includes a piston, a perforated piston, a first end with a first opening, and a second end with a second opening. The method includes:

-   -   (a) introducing the second fluid into the chamber;     -   (b) introducing a third fluid into the first end of the chamber         through the first opening to move the piston towards the         perforated piston and the second end of the chamber so that the         piston injects at least a portion of the first fluid through the         one or more channels of the perforated piston and into the         second fluid;     -   (c) removing the third fluid through the first opening using a         restrictor that partially restricts the flow of the third fluid         through the first opening to move the piston away from the         perforated piston and towards the first end of the chamber; and     -   (d) repeating processes (b) and (c) one or more times to form a         mixture between the first fluid and the second fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings:

FIG. 1 shows a mixing apparatus in accordance with one embodiment of the present disclosure;

FIGS. 2A and 2B show a restrictor in accordance with one embodiment of the present disclosure;

FIGS. 3A-3E show a method for mixing fluids in accordance with one embodiment of the present disclosure;

FIG. 4 shows a wireline logging system at a well site in accordance with one embodiment of the present disclosure;

FIG. 5 shows a wireline tool in accordance with one embodiment of the present disclosure; and

FIG. 6 shows the wireline tool of FIG. 5 in more detail.

DETAILED DESCRIPTION

Illustrative embodiments of the present disclosure are directed to an apparatus for mixing a first fluid with a second fluid. The second fluid can be a formation fluid that includes a gas, a liquid, or both. The first fluid can be a reactant fluid that reacts when mixed with the formation fluid to detect presence of a particular chemical species within the formation fluid (e.g., hydrogen sulfide (H2S), carbon dioxide (CO2), and mercury (Hg)). The mixing apparatus described herein includes a restrictor that protects components of the mixing apparatus during operation. Details of various embodiments are described below.

FIG. 1 shows an example of a mixing apparatus 100 for mixing a first fluid with a second fluid. The mixing apparatus 100 includes a chamber 102 with a first end 104, a second end 106, an opening 108 at the first end, and a second opening 110 at the second end. The apparatus 100 also includes a piston 112 positioned within the chamber. The piston 112 generates a seal between the first end 104 and the second end 106 of the chamber and is movable along the chamber towards the first end and towards the second end of the chamber. The apparatus 100 further includes a restrictor 114 positioned at the first end of the chamber. The restrictor 114 allows the flow of fluid through the first opening 108 and into the chamber 102 and partially restricts flow of fluid through the first opening and out the chamber. Furthermore, the apparatus also includes a perforated piston 118 positioned within the chamber 102 between the piston 112 and the second end 106 of the chamber. The perforated piston 118 includes a bottom surface, a top surface, and one or more channels that allow fluid to flow between the top surface and the bottom surface of the perforated piston. In some embodiments, the perforated piston 118 is affixed to walls of the chamber and is stationary. In other embodiments, the perforated piston 118 is movable along the chamber 102 towards the first end and towards the second end of the chamber.

The mixing apparatus 100 also includes a fluid delivery system for providing fluids to the chamber. In this embodiment, the fluid delivery system include a valve 120 in fluid communication with the second opening 110 and a pump 122 in fluid communication with the first opening 108. The fluid delivery system moves the piston 112 towards the first end 104 of the chamber 102 and thus supplies a volume of the second fluid to the chamber through the second opening. In some embodiments, the first fluid is pre-loaded within the chamber 102. In other embodiments, the fluid delivery system first introduces the first fluid into the chamber 102 and then introduces the second fluid. The fluid delivery system also moves the piston 112 towards the perforated piston 118 and the second end 106 of the chamber to inject at least a portion of the first fluid through the one or more channels of the perforated piston 118 and into the second fluid.

Movement of the piston 112 can be accomplished by using the pump 122 to introduce a third fluid (e.g., water) into the first end 104 of the chamber. The third fluid is used to hydraulically push on the piston 112 and move the piston towards the perforated piston 118 and the second end 106 of the chamber. Also, the piston 112 can move back towards the first end 104 of the chamber by removing the third fluid from the chamber 102 through the restrictor 114. The third fluid can be removed using the pump 122 or by opening a valve (not shown) that creates a pressure difference between the first end of the chamber 104 and the second end of the chamber 106. For this reason, the first end 104 of the chamber can be referred to as the “hydraulic end.”

FIGS. 2A and 2B show the restrictor 114 in more detail. The restrictor 114 allows flow of fluid in a first direction (into the chamber 102) while partially restricting flow of fluid in an opposite direction (out of the chamber), as compared to the first direction. The restrictor 114 can also be referred to as a “restrictor piston” because the restrictor can be part of a piston that is positioned at the first end 104 of the chamber. In the specific example shown in FIG. 2, the restrictor 114 includes two passage ways. A first passage way 202 includes a small hole that provides a flow path of high resistance from the chamber 102 to first opening 108. A second passage way 204 includes a constriction within the passage way. A ball with a diameter that is larger than the constriction is positioned within the passage way 204. This configuration can be referred to as a “ball check valve” configuration. Other check valves can also be used within the second passage way 204. For example, diaphragm check valves, swing check valves, lift-check valves, in-line check valves, or duckbill valves can also be used. When in an open position, the second passage way 204 provides for greater fluid flow than the first passage way 202.

FIGS. 2A and 2B show the two states of fluid flow through the restrictor 114. In FIG. 2A, when the third fluid is flowing out of the chamber 102 and through the first opening 108, the ball lodges within the constriction and prevents the flow of fluid through the second passage way 204. In this state, however, the first high resistance passage way 202 remains open and the third fluid flows through the first passage way. In FIG. 2B, when the third fluid is flowing into the chamber 102 and through the first opening 108, the ball is dislodged from the constriction and the third fluid flows through the second passage way 204, while also flowing through the first passage way 202. In this manner, the restrictor 114 allows the flow of fluid into the chamber 102, while partially restricting flow of fluid out the chamber.

In FIG. 1, the restrictor 114 and the first opening 108 are separate components. The third fluid first flows through the restrictor and then through the first opening 108, or vice versa. In other embodiments, the restrictor 114 and the first opening 108 are the same components. The one or more passageways within the restrictor 114 are the first opening 108.

FIGS. 3A-3E show a method for mixing a first fluid with a second fluid using the mixing apparatus 100 shown in FIG. 1. In FIG. 3A, the pump 122 draws the piston 112 down towards the first end 104 of the chamber and, thereby, pulls the second fluid 300 into the chamber 112. As explained above, in some embodiments, the first fluid (e.g., reactant) 302 is pre-loaded within the chamber 102 and there is no need for the pump to introduce the first fluid into the chamber. In other embodiments, the pump 122 can be used to introduce the first fluid into the chamber 102 and then introduce the second fluid. Once the second fluid has been introduced, in some embodiments, the valve 120 is closed.

In. FIGS. 3B and 3C, the pump 122 pushes up on the piston 112 by introducing a third fluid (e.g., water) 304 into the first end 104 of chamber through the restrictor 114. Because the third fluid 304 is flowing into the chamber 102, the restrictor 114 allows the fluid to flow through both passage ways 202, 204. When the piston 112 moves, the piston forces the fluid (e.g., the first fluid, the second fluid, or both) through the channels in the perforated piston 118 and mixes the fluids to generate a fluid mixture. By forcing the fluid through the perforated piston, a spray effect is generated in the chamber 102. In particular, a spray of droplets is formed when the first fluid is injected into the second fluid. This spray effect increases the surface area of the second fluid 300 coming in contact with the first fluid 302 for more thorough mixing. The spray effect also provides agitation that ensures that that the fluid mixture becomes homogenous.

In FIG. 3D, the chamber 102 is vented to lower from the first end 104 of the chamber 102. For example, a valve (not shown) is opened and this causes a large pressure drop during equalization that is controlled by the restrictor 114 at the first end 104 of the chamber. In this case, because the third fluid 304 is flowing out of the chamber 102, the restrictor closes the second passage way 204 and partially restricts the fluid flow. The third fluid 304 is directed to the first high resistance passage way 202 and is slowly released. Thus, the restrictor 114 allows the piston 112 to descend in a controlled manner by restricting the rapid exit of the third fluid 304 from the chamber. The controlled descent of the piston 102 prevents damage to the piston and prevents slippage in the position of the perforated piston 118 (in embodiments where the perforated piston is movable).

The processes in FIGS. 3B, 3C, and 3D can be repeated a plurality of times to ensure a thorough mixing process (e.g., to ensure that the fluid mixture becomes homogenous). Once the mixing is complete, in some embodiments, the valve 120 is open.

In FIGS. 3A, 3B, 3C, and 3D, the perforated piston 118 remains stationary. Then, in FIG. 3E, the perforated piston 118 and the piston 112 are pushed to the second end 106 of the chamber using the pump 122 so that the fluid mixture is pushed out of the chamber. The fluid mixture can then be analyzed optically by a fluid analyzer, such as a spectroscopic cell. In some embodiments, the fluid mixture can be analyzed optically by a fluid analyzer while still within the chamber 102.

Illustrative embodiments of the present disclosure are directed to oilfield applications. FIG. 4 shows one example of a wireline logging system 400 at a well site. The wireline logging system 400 can be used to mix formation fluids with reactant fluids to detect particular chemical species within the formation fluids. In this example, a wireline tool 402 is lowered into a wellbore 404 that traverses a formation 406 using a cable 408 and a winch 410. The wireline tool 402 is lowered down into the wellbore 404 and makes a measurement of the adjacent formation 406 at one or more sampling locations along the wellbore 404. The data from these measurements is communicated through the cable 408 to surface equipment 412, which may include a computer system for storing and processing the data obtained by the wireline tool 402. In this case, the surface equipment 412 includes a truck that supports the wireline tool 402. In another embodiment, however, the surface equipment may be located within a cabin on an off-shore platform.

FIG. 5 shows another view of the wireline tool 402. The wireline tool 402 includes a selectively extendable fluid admitting assembly (e.g., probe or packer) 502. This assembly 502 extends into the formation 406 and withdraws formation fluid from the formation 406 (e.g., samples the formation) and into the wireline tool 402. The formation fluid flows through the assembly 502 and into a main flow line 504 within a housing 506 of the tool 402. A pump (not shown) can be used to withdraw the formation fluid from the formation 406 and pass the fluid through the main flow line 504. The wireline tool 402 may also include a selectively extendable anchoring member 508 that is arranged to press the probe 502 assembly against the formation 406. The wireline tool 402 also includes a fluid analyzer module 510 for analyzing at least a portion of the fluid in the flow line 504. The fluid analyzer 510 can be an optical or spectroscopic cell that is used to optically measure and determine characteristics of the fluid within the flow line 504 (e.g., optical density and/or composition).

FIG. 6 shows the wireline tool 402 in further detail. The wireline tool 402 includes a mixing apparatus 100 for mixing a first fluid with a second fluid, such as the one shown in FIG. 1. The wireline tool 402 includes a fluid delivery system. The fluid delivery system includes two lines 602, 604 that connect the main flow line 504 to different ends 104, 106 of the mixing apparatus 100. The fluid delivery system also includes a pump 606, a top valve 608, a bottom valve 610, a wellbore valve 612, and a second end valve 614.

Operation of the fluid delivery system shown in FIG. 6 is described with respect to FIGS. 3A-3E. The process described below occurs downhole within a wellbore tool. In FIG. 3A, (i) top valve 608 and wellbore valve 612 are closed, (ii) second end valve 614 and bottom valve are open, and (iii) the pump 606 draws the piston 112 down towards the first end 104 of the chamber by pulling the third fluid 304 (e.g., formation fluid and/or drilling mud) out of the chamber 112. As the piston is drawn down, a sample of formation fluid 300 enters the second end 106 of the chamber 102. As explained above, in some embodiments, the reactant 302 is pre-loaded within the chamber 102 and there is no need to introduce the reactant into the chamber. In other embodiments, a separate reactant bottle and valve assembly can be used to introduce the reactant into the chamber 102 and then introduce the formation fluid.

Once the formation fluid has been introduced, in. FIGS. 3B and 3C, the second end valve 604 is closed and the pump 606 pushes up on the piston 112 by reintroducing the third fluid 304 into the first end 104 of the chamber through the restrictor 114. Because the third fluid 304 is flowing into the chamber 102, the restrictor 114 allows the fluid to flow through both passage ways 202, 204. When the piston 112 moves, the piston forces fluid (e.g., the formation fluid, the reactant fluid, or both) through the channels in the perforated piston 118 and mixes the fluids to generate a fluid mixture. By forcing the fluid through the perforated piston, a spray effect is generated in the chamber 102. In particular, a spray of droplets is formed when the reactant fluid is injected into the formation fluid. This spray effect increases the surface area of the reactant fluid 300 coming in contact with the formation fluid 302 for more thorough mixing. The spray effect also provides agitation that ensures that that the fluid mixture becomes homogenous.

In FIG. 3D, the chamber 102 is vented to lower pressure (e.g., pressure within the wellbore 404) from the first end 104. For example, the wellbore valve 612 is open to the wellbore environment 404 while the top valve 608 is closed. The first end 104 of the chamber is thus exposed to wellbore pressure. This causes a large pressure drop and pressure equalization that is controlled by the restrictor 114 at the first end 104 of the chamber. In this case, because the third fluid 304 is flowing out of the chamber 102, the restrictor closes the second passage way 204 (as shown in FIGS. 2A and 2B) and partially restricts the fluid flow. The third fluid 304 is directed to the first high resistance passage way 202 and is slowly released. Thus, the restrictor 114 allows the piston 112 to descend in a controlled manner by restricting the rapid exit of the third fluid 304 from the chamber. The controlled descent of the piston 102 prevents damage to the piston and prevents slippage in the position of the perforated piston 118.

The processes in FIGS. 3B, 3C, and 3D can be repeated a plurality of times to ensure thorough mixing between the formation fluid and the reagent fluid (e.g., to ensure that the fluid mixture becomes homogenous).

Once the mixing is complete, in FIG. 3E, the perforated piston 118 and the piston 112 are pushed to the second end 106 of the chamber by opening the bottom valve 510 while keeping the top valve closed 608. In this manner, the fluid mixture is pushed into the main flow line 504 where it can be analyzed using the fluid analyzer 510. The fluid analyzer 510 can detect whether there has been a reaction between the formation fluid and the reactant fluid. For example, in some cases, the reactant fluid and a particular chemical within the formation fluid can react and cause the fluid's optical absorbance to increase. This increase in optical absorbance in then detected by the fluid analyzer 510. The increase in absorbance indicates the presence of the particular chemical within the formation fluid.

The restrictor 114 allows the piston 112 to descend in a controlled manner by restricting the rapid exit of the third fluid 304 from the chamber 102 through the first opening 108. Without the restrictor 114, when the first end 104 of the chamber is opened to the wellbore pressure, the pressure imbalance would force the third fluid 304 out of the chamber, thereby, forcibly impacting the piston 112 against the first end 104 of the chamber and also potentially shifting the position of the perforated piston 118 within the chamber. Damage to the piston 112 and/or movement of the perforated piston 118 may render the apparatus inoperable for subsequent mixing cycles.

The descent of the piston 112 can also be controlled by the pump 606. However, to repetitively perform the processes shown in FIGS. 3B, 3C, and 3D, the pump 606 would switch flow direction many times (e.g., into and out of the chamber), which is harsh on the pump and may reduce the life of the pump or render the pump inoperable. The restrictor 114 can be used to control the descent of the piston 112 without using the pump 606 to reverse the flow of fluid multiple times.

Further details regarding the chamber 102, the piston 112, the perforated piston 118, the fluid delivery system, the reactant fluids, and methods for mixing are described in U.S. Pat. No. 8,708,049, issued on Apr. 29, 2014, which is incorporated herein by reference in its entirety.

In various embodiments, the first fluid or the second fluid can be a liquid or a compressible fluid, such as a gas. The first fluid or the second fluid can be a sample fluid such as a formation fluid that is withdrawn from a subterranean formation. Also, the first fluid or the second fluid can be a reactant fluid. The reactant fluid can be used to detect various chemicals, such as hydrogen sulfide (H2S), carbon dioxide (CO2), and mercury (Hg) within another fluid. For example, the reactant fluid can use metal ions to react with a particular chemical within a sample fluid, such as a formation fluid. Further details regarding reactant fluids are provided in U.S. Patent Application Publication 2012/0276648, published on Nov. 1, 2012, and U.S. Patent Application Publication 2012/0149117, published Jun. 14, 2012. Both of these applications are hereby incorporated herein by reference in their entireties.

Illustrative embodiments of the present disclosure are not limited to wireline logging operations, such as the ones shown in FIGS. 4 and 5. For example, the embodiments described herein can also be used with any suitable means of conveyance, such coiled tubing or drill pipe. Furthermore, various embodiments of the present disclosure may also be applied in logging-while-drilling (LWD) operations, sampling-while-drilling operations, measuring-while-drilling operations, production logging operations, or any other operation where sampling of formation fluid is performed.

Although several example embodiments have been described above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the scope of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure. 

We claim:
 1. A wellbore tool for mixing a first fluid with a second fluid, the wellbore tool comprising: a chamber having a first end, a second end, a first opening at the first end, and a second opening at the second end; a piston positioned within the chamber, wherein the piston generates a seal between the first end and the second end of the chamber and is movable along the chamber towards the first end and towards the second end of the chamber; a restrictor positioned at the first end of the chamber and configured (i) to allow the flow of fluid through the first opening and into the chamber and (ii) to partially restrict flow of fluid through the first opening and out the chamber; and a perforated piston positioned within the chamber between the piston and the second end of the chamber, wherein the perforated piston comprises a bottom surface, a top surface, and one or more channels that allow fluid to flow between the top surface and the bottom surface of the perforated piston.
 2. The wellbore tool of claim 1, the first fluid is pre-loaded within the chamber.
 3. The wellbore tool of claim 1, further comprising: a fluid delivery system configured (i) to move the piston toward the first end of the chamber in order to supply a volume of the second fluid to the chamber through the second opening and (ii) to move the piston towards the perforated piston and the second end of the chamber to inject at least a portion of the first fluid through the one or more channels of the perforated piston and into the second fluid.
 4. The wellbore tool of claim 1, wherein the second fluid is compressible.
 5. The wellbore tool of claim 1, wherein the second fluid is a formation fluid that comprises a gas, a liquid, or some combination thereof
 6. The wellbore tool of claim 1, wherein the first fluid is a reactant fluid.
 7. The wellbore tool of claim 6, wherein the reactant fluid is detects at least one of H₂S, CO₂, and Hg within the second fluid.
 8. The wellbore tool of claim 1, wherein the second fluid is a formation fluid and the wellbore tool further comprises: a fluid admitting assembly for extending into a formation and withdrawing the formation fluid from the formation and into the wellbore tool.
 9. The wellbore tool of claim 1, further comprising: a fluid analyzer configured to analyze a mixture of the first fluid and the second fluid.
 10. A downhole method for mixing a first fluid with a second fluid within a chamber that comprises a piston, a perforated piston, a first end with a first opening, and a second end with a second opening, the method comprising: (a) introducing the second fluid into the chamber; (b) introducing a third fluid into the first end of the chamber through the first opening to move the piston towards the perforated piston and the second end of the chamber so that the piston injects at least a portion of the first fluid through the one or more channels of the perforated piston and into the second fluid; (c) removing the third fluid through the first opening using a restrictor that partially restricts the flow of the third fluid through the first opening to move the piston away from the perforated piston and towards the first end of the chamber; and (d) repeating processes (b) and (c) one or more times to form a mixture between the first fluid and the second fluid.
 11. The downhole method of claim 10, further comprising: (e) moving the piston toward the second end of the chamber so that the fluid mixture exits the chamber through the second opening.
 12. The downhole method of claim 10, wherein the perforated piston remains stationary during process (a) through process (d).
 13. The downhole method of claim 10, wherein the first fluid is a recant fluid and the second fluid is a formation fluid.
 14. The downhole method of claim 10, wherein, at process (b), a spray of droplets is formed when the first fluid is injected into the second fluid.
 15. The downhole method of claim 10, wherein the second fluid is a formation fluid that comprises a gas, a liquid, or some combination thereof
 16. The downhole method of claim 10, the first fluid is pre-loaded within the chamber.
 17. The downhole method of claim 10, wherein process (a) through process (d) are performed within a wellbore tool.
 18. The downhole method of claim 17, further comprising: withdrawing the formation fluid from a formation and into the wellbore tool. 